Chemical compounds can exist in forms that are mirror images of each other. Like gloves, they can be either left-handed or right-handed.
Sugars are such "handed" molecules. Human digestive enzymes have evolved to act upon right-handed sugar molecules, while often allowing left-handed forms to pass directly through.
Both l-tagatose, the left-handed form, and d-tagatose, the right-handed form, are approximately as sweet as table sugar. Gilbert Levin's researchers at Biospherics Inc. originally investigated l-tagatose, but later they hit upon d-tagatose as a potentially better candidate. D-tagatose is metabolized by the body and thus puts no extra load on the kidneys. And, lab officials say, it doesn't appear to create fat, as most sugars do, possibly because of the rate at which it metabolizes.
--M.C.
